1. Field of the Invention
This invention relates to a method of forming a conductive film on a surface of an insulating region of a substrate, which method is suitable to, for example, producing an interconnection of a semiconductor device.
2. Description of the Prior Art
In a conventional method of manufacturing an integrated circuit, the following steps are ordinarilly performed to form an electrical interconnection.
First, an insulating film of SiO.sub.2 provided with a contact hole is formed on a silicon substrate having an element region such as an impurity-diffused layer. Secondly, a thin aluminum film, is deposited on the entire overall surface of the insulating film using a sputter-deposition technique. A photo-resist is coated on the thin aluminum film. Then, a patterned mask is arranged facing the photo-resist layer and separated therefrom by a predetermined distance. A light beam is irradiated on the photoresist layer through the patterned mask, and the photo-resist layer is selectively exposed. Then, unnecessary parts of the photo-resist layer are removed, and part of the aluminum film is exposed. The exposed part of the aluminum film is removed by sputter-etching, etc., using the remaining resist layer as an etching mask. The resist layer is removed, and the interconnecting process ends.
In the above method, the number of manufacturing steps is large to form only one layer interconnection. Therefore, the manufacturing yield is low, and the manufacturing time is long. Especially, the problem of long manufacturing time is serious in producing an integrated circuit such as the so-called GATE ARRAY, where the interconnections are personalized after receiving a client's order. In addition, the conventional method exhibits poor reproducibility of the interconnections, due to the complicated effects of inaccuracies during exposing and etching.
For this reason, a design tolerance for interconnecting accuracy is required, which makes it difficult to attain a high density integrated circuit.
Another method of forming an electrical interconnection is known from Japanese Patent Publication (KOKAI) No. 52-40969. In this known method, a selective chemical vapor deposition process is adopted to form the interconnection. The steps of this method include forming a silicondioxide film with a contact hall on a silicon substrate, and then applying a selective chemical vapor deposition process. In the process, a gas such as M.sub.0 F.sub.6 or WF.sub.6 and a hydrogen gas are introduced, while the substrate is heated. Thereby, a molybdenum or tungsten layer is deposited on exposed part of the substrate surrounded by the contact hall, but is not deposited on the silicon-dioxide film. Then, in order to lead out the molybdenum or tungsten layer, an aluminum interconnection pattern is essentially formed on the silicon-dioxide film. According to this above method, the number of manufacturing steps is large, and the reproducibility and yield are bad. This is because the step of forming the aluminum interconnection pattern is essential, which complicates the manufacturing of an integrated circuit, etc.